This invention relates generally to a slotted insert which can be embedded in concrete to provide a framing system to which brackets and fittings can be fastened at any point. With such framing system components, racks, supports for pipes, wiring and electrical equipment, machine frames and a limitless variety of structures can be affixed to walls, ceilings or other forms. More particularly it relates to an improved slotted channel device compatible with other components of a "strut" type bolted framing system, known generically as "strut systems". Such strut systems have been in large use for many years.
The conventional concrete insert in use in the strut system is a channel with two parallel sides extending to the bottom of the channel with inturned lips at the front edge. Such sides are parallel so that fittings may be fastened to the front slot by means of a rectangular nut with beveled ends which, when inserted into the channel slot, is restricted from turning beyond 90.degree. by the interior channel walls. This restriction positions the nut properly so that, when tightened, its surface serrations and teeth within the serrations engage the inturned lips of the channel. The disadvantage of such inserts with parallel sides throughout is that they must either be pierced from the rear to form anchors (hooks) or have anchors (hooks) welded to the rear or sides to provide a holding means within the concrete. The hooks have sharp edges which are hazardous to workmen. In some cases the hooks interfere with reinforcing bars and other buried reinforcements or conduits in the concrete. In such cases the installers have no alternative but to bend the hooks to avoid the obstruction, which action reduces the loading capability of the hook type insert at that point and creates a hidden hazard when loads are connected at these hidden points so that the manufacturer's published load figures cannot be relied upon. Furthermore, the sharp metal edges on the hook type inserts can affect the integrity of the concrete in which they are embedded since these edges act as "stressrisers" and lower the capacity of the surrounding concrete. This is especially critical in concrete having lower compressive strength.
The concrete insert of the present invention, having a front section of parallel sides to receive the same rectangular nut and rear wedge shape section to serve as an anchor in the concrete, completely eliminates the anchor hooks. All surfaces are smooth and free from sharp edges which provide a safety feature for the installers. It has also been found that this concrete insert offers greater load bearing capacity when installed than other inserts compatible with bolted framing systems. In addition such insert can be installed in concrete without interfering with other buried reinforcements or conduits in the concrete. Since there are no hooks projecting from the insert it is particularly suitable for installation in concrete pours of shallow depth or where interference may be caused by buried reinforcements or buried conduits.
U.S. Pat. Nos. 1,878,921, 1,988,124 and 2,780,936 disclose anchors for concrete which have wedge shapes, but do not provide the parallel side walls at the front portion to make them compatible with the bolted strut system heretofore described.